Binding of protein A to some human gamma-globulins used intravenously

We examined the binding capacity of radioiodinated protein A ([125I]PA) for several human IgG immunoglobulins. Most of them are commercial preparations used in immunosubstitution therapy. Two experimental approaches were chosen. In the first, the binding of [125I] PA to solidified IgG preparations was studied. In the second approach, the inhibition of [125I] PA binding to a given immunoglobulin by various human immunoglobulin samples was established. Both the binding and inhibition criteria were used to estimate the order of the relative binding capacities of the Fc region in studied IgG preparations. The various commercial gamma-globulin preparations were also compared using single radial immunodiffusion and cross-immunoelectrophoretic techniques.